This invention relates to a mounting structure for ball joints which are adapted to connect between two structural members such as the upper and lower arms of the suspension mechanism in a vehicle, for example and more particularly, to a mounting device for mounting such a ball joint in the lower arm of the above type in a simple and reliable manner. This invention also relates to a method for mounting the ball joint in the lower arm of the vehicular suspension mechanism in a simple and reliable manner.
The ball joint of the above type has a hollow cylindrical housing formed of sheet metal which is adapted to be held in position within the cylindrical portion of the lower arm. Various structures for mounting the ball joint of the above type in the lower arm have been proposed and practically employed and such conventional ball joint mounting devices will now be described referring to FIGS. 1 through 4 of the accompanying drawings. The ball joint mounting structure of FIG. 1 comprises an annular flange 12 provided adjacent to one or the upper end (as seen in FIG. 1) of the hollow cylindrical housing 11 of a ball joint 10 radially and outwardly extending from the housing 11 and a knurled portion 13 provided in the outer periphery of the housing 11 between the opposite ends of the housing. In mounting the ball joint 10 in one of two structural members to be joined together by the ball joint such as the lower arm 14 of the suspension mechanism of a vehicle, for example, the knurled portion 13 of the ball joint housing 11 is press fitted in the cylindrical portion 15 of the lower arm 14 until the flange 12 abuts against the lower arm cylindrical portion 15.
The ball joint mounting structure of FIG. 2 is substantially similar to the device of FIG. 1 except that the device further includes a snap ring 16 adjacent to the end opposite from the flange 12 which is adapted to be fitted on the cylindrical portion 15 after the ball joint housing 11 has been press fitted in the lower arm 14 in the manner mentioned hereinabove in connection FIG. 1 to thereby hold the ball joint in position within the lower arm.
In the ball joint mounting structure of FIG. 3, in place of the snap ring 16, a threaded portion 17 is formed in the outer periphery of the cylindrical ball joint housing 11 between the opposite ends of the housing and a mating threaded portion 17' is formed in the inner surface of the cylindrical portion 15 of the lower arm 14. In mounting the ball joint 10 in the lower arm 14, the ball joint housing 11 is threaded into the threaded portion 17' of the lower arm 14 to secure the ball joint to the lower arm.
The ball joint mounting structure of FIG. 4 is substantially similar to the device of FIG. 1 except that a weld 18 is formed between the lower edge of the wall of the lower arm cylindrical portion 15 and the end of the ball joint housing 11 opposite from the flange 12 to thereby hold the ball joint 10 in position within the lower arm.
However, the ball joint mounting structure of FIG. 1 has the disadvantage that the ball joint housing 11 easily comes off the lower arm 14 and the ball joint mounting structure of FIG. 2 has the disadvantages that the device requires an additional processing step to provide an annular groove in the ball joint housing 11 for receiving the snap ring 16 and the distance between the groove and flange 12 is required to be precisely determined resulting in an increase in production cost. Furthermore, in the ball joint mounting device of FIG. 2, the housing 11 is required to be subjected to heat-treatment or high frequency induction hardening so that the snap ring receiving groove will have high strength. The ball joint mounting structure of FIG. 3 has the disadvantage that since the housing of the ball joint and the cylindrical portion of the lower arm are provided with threaded portions and the threaded portions are required to be subjected to high frequency induction hardening, the processing of the structure requires a substantial time resulting in an increase in production cost. The ball joint mounting structure of FIG. 4 has the disadvantages that the structure requires a troublesome operation such as welding and if the bearing of the ball joint is formed of synthetic resin, the welding can not be carried out because the high temperature derived from the welding increases the temperature of the ball joint to a substantially high value and causes degeneration of lubricant.